A variety of optical devices include an active component such as a light sensor or modulator. These active components typically guide a light signal through a component waveguide while an electrical field is applied to the component waveguide. The component waveguide can be partially defined by a ridge that extends upwards from slab regions. The performance of these components is often very sensitive to the thickness of these slab regions. Since these slab regions are generally formed by etching, the thickness of the slab regions is difficult to control. As a result, the performance of different active devices is often inconsistent. The inconsistency of these optical devices can provide an undesirably large level of waste in the fabrication process.
For the above reasons, there is a need for optical devices having consistent performance.